The objective of this study is to improve understanding of an emerging drug trend: heroin users who do not shift to injecting but who enter treatment as inhalers. Previous studies indicate that these users may be a population which is different from heroin injectors. Admissions of heroin inhalers to treatment have increased in recent years and compared to heroin injectors, these patients enter treatment after a shorter period of heroin use. There are also other demographic and situational differences between inhalers compared to injectors. This study will investigate key questions that are important for improving the knowledge base for treatment programs to deal with the problems that bring these persons to seek help. This study will undertake preliminary research to investigate the following questions: 1) What are the predictors of heroin inhaling versus injecting at onset of use, and at the time of admission to treatment? 2) What predicts differential entry rates into treatment for heroin inhalers and injectors? 3) What is the typical pattern of use and "career" (usage history) of heroin inhalers? 4) What are the health service needs of these inhalers? This project will compare heroin inhalers and injectors entering treatment programs statewide through analysis of the state's client data system and by obtaining assessment and psychosocial information from client files of programs in four Texas cities. In-treatment heroin inhalers and a matched group of heroin injectors will be interviewed about factors related to initiation of use, patterns and history of use, individual and social perceptions, health needs, and problems leading to treatment. Focus groups of heroin inhalers and injectors in treatment and inhalers both in and out of treatment will be held to obtain explanatory information about these preliminary findings and to obtain information concerning barriers to treatment, treatment experiences, and attitudes toward treatment.